Containers are used in the transportation and temporary storage of virtually all types of goods and materials. Usually, these containers have dimensions of 8'.times.8'.times.20', although 30' and 40' containers are also used. Apparatus for handling such containers include bridge cranes, stradle carriers, and forklift trucks.
Bridge cranes are permanent installations which are used at locations such as harbors to move containers onto and off of ships and barges. Although satisfactory for the intended purpose, bridge cranes cannot transport and handle containers at remote locations.
Stradle carriers are high, wide devices which carry containers in an elevated orientation. For this reason, stradle carriers tend to tip over when operated on soft or inclined surfaces.
In order to transport a container by means of a forklift truck, the length of the container must extend transversely to the direction of movement. This requires unnecessarily wide roadways, gates, and doorways, and may present a safety problem, since the forklift truck operator sometimes cannot see around the container during forward movement.
These problems become even more critical when containers are used in military applications. For example, landing craft are typically used to transport war materiel to beachheads. Stradle carriers are too large to enter landing craft, and the landing craft doors are not wide enough to permit the removal of containers in a sideways orientation. Also, neither stradle carriers nor forklift trucks are adapted for operation in surf, or on sand, or on steep surfaces often found at beachheads.
For these reasons, the present practice is to use a two-wheel trailer, pulled by a bulldozer or similar device, to remove containers from landing craft and to move the containers through the surf and across the beach to a suitable location. At this point, a stradle carrier, a forklift truck, or a crane places the container on a truck. The truck then hauls the container to its ultimate destination, where a second forklift truck or stradle carrier removes the container from the truck. Up to five pieces of equipment may be required to move a container from the interior of a landing craft to its ultimate destination.
Even at installations such as military bases, current procedures for handling containers are unsatisfactory. Containers are typically received at a central location from railroad cars or semi-trailers. Due to space limitations, neither stradle carriers nor forklift trucks can be used to transport the containers from the central receiving lcoation to the ultimate destinations, such as mess halls or ammo dumps. It is therefore necessary to unload each container at the central receiving location and to use trucks to transport the container contents to the ultimate destinations.
The present invention is a container handling apparatus which overcomes these and other problems long associated with the prior art. The container handling apparatus of the invention can transport containers across adverse terrain, such as through surf, across beaches, and over highly inclined surfaces. The apparatus of the present invention can also transport containers across obstacles such as rocks, logs, craters, ditches, and rubble. A container handling apparatus incorporating the invention can operate at speeds of up to 45 m.p.h. unloaded, and up to 25 m.p.h. loaded. Finally, the present invention can transport containers through relatively limited spaces, thereby facilitating both the removal of containers from landing craft and the positioning of containers at ultimate destinations, without unloading the contents of the containers onto trucks.
The container handling apparatus of the invention has a pair of elongated side frames, connected at the forward end by a cross frame. The frames are propelled and supported by a plurality of wheels, which are driven by a drive means.
The apparatus has four lift mechanisms for attachment to a container. Each lift mechanism is pivotally connected to one end of a secondary lift arm. Each lift mechanism has a tab for insertion into a slot on the container, and means for raising and lowering the lift mechanism relative to the secondary lift arm.
A cam follower is mounted on the lower end of each secondary lift arm. A plurality of cams guide each cam follower horizontally along one of the side frames. Each secondary lift arm is angled to avoid intersection with the other secondary lift arm.
A primary lift arm is pivotally connected to the midpoint of each secondary lift arm. The other end of each primary lift arm is pivotally connected to one of the side frames at a pivot connection. Each secondary lift arm is twice as long as each primary lift arm.
A power means, such as a plurality of hydraulic cylinders, rotates the primary lift arms about the pivot connections between the primary lift arms and the side frames. This causes the upper ends of the secondary lift arms to move vertically to raise and lower the lift mechanisms and the container. Equalizing means determines the position of each primary lift arm and automatically keeps the positions of the four lift mechanisms at the same height.